If you’re a developer considering what and where to build on your site, you’ll need to know firstly, what utilities are already present, and secondly, where best to locate the new services for your proposed development and how low these services can go.
The requisite depth of your utility apparatus will vary depending on its type and location (e.g. in a road, a footpath or within private land).
The services must be laid in accordance with strict guidelines, to avoid:
- Safety hazards (gas leaks or electrocution)
- Accidental damage during excavation works
- Service disruptions
- Costly repairs and legal liabilities
- Environmental damage
And to allow:
- Accessibility for maintenance
- Sufficient separation between each service (if the location is a shared trench)
Guidance and legislation
Useful sources of information include:
- Street Works UK Guidance (2023, Issue 1) – it sets out recommendations for minimum depths, radial separation and trench sharing for utilities;
- The National Joint Utilities Group (NJUG) – it has published guidelines on the positioning and colour coding of underground services;
- The Health and Safety Executive (HSE) methodology – it provides land use planning advice with respect to potential risks and hazards resulting from excavation works; and
- The Utilities Act 2000 – it set up regulatory bodies (such as Ofgem), and outlines the duties and responsibilities of utility providers.
From a developer’s point of view, the following recommended depths are worth bearing in mind:
Water mains
Colour coded blue, and generally laid below ground at a depth of 750 to 1,350 mm (to prevent freezing and subsequent damage to the pipes).
Gas mains
Colour coded yellow, and usually laid at 750 mm (under roads or verges) or 600 mm (under footpaths). Gas mains are subject to strict health and safety regulations, known as PADHI guidelines (Planning Advice for Developments near Hazardous Installations), and have to be buried deep enough to protect them from surface heat.
Gas service pipes
Usually laid at a minimum depth of 375 mm in private ground, or 450 mm in footpaths and highways.
Electricity cables
Colour coded red if they’re high voltage and black if they’re low voltage, these are normally laid at a depth of 900 mm but this can vary depending on their voltage and the location (e.g. bridges can have cables 100 mm below the surface, while National Grid cables can be laid at a depth of 1,200 mm in ploughed fields).
Telecommunications/broadband cables
Colour coded green, and generally located in footpaths or private land. These cable are usually found at a depth of 250 to 350 mm.
The depths above are general guidelines, and you should always consult the relevant utility provider beforehand. Utility maps and cable locators should be used prior to digging and compliance with HSE and Utilities Act regulations is essential.
